Many modern high performance engines generate extremely hot exhaust gas emissions. As these emissions are expelled from the engine and pass through the exhaust manifold, the hot emissions heat the exhaust manifold or pipes to increasingly high temperatures. Such high temperatures cause the temperature of the components in the manifold, i.e. stampings, to elevate resulting in thermal expansion and discoloration of the components.
To account for the effects of high-temperature gas emissions, some manifold designs employ a dual wall construction that utilizes an air gap between inner and outer components. In some instances the air gap may be created using spacers or may be designed with a first wall and second wall spaced apart from one another. The resulting air gap between the walls insulates the outer wall from the inner wall thereby reducing heat transfer to the outer wall. As a result, expansion, discoloration and excessive heating at the outer wall are minimized.
In engines having a turbocharger, the manifold is commonly connected to a turbine housing. The turbine housing may utilize the engine's exhaust to spin a turbine, which in turn spins an air pump to compress air. The compressed air is pumped into the cylinders during combustion. The turbine housing typically includes an inlet for receiving the engine's exhaust.
Some manifold/turbine housing configurations utilize a unitary body, meaning a single formed piece comprising the manifold and turbine housing. Commonly, however, the manifold and housing are separate parts. Designs that utilize a separate housing and manifold allow for replacement of system components as well as individual material choices for each component of the system. Such designs, however, may require a coupling between the manifold and the turbine housing.
Like the manifold, portions of the turbine housing may include a dual wall configuration. For example, the housing may include a dual wall portion having an air gap at or near its inlet. Therefore, the coupling between the manifold and turbine housing must account for the dual wall geometries of both the manifold and the housing.
Traditional manifold to housing couplings suffer from several deficiencies. For example, as described above, heat from the engine may cause the inner walls of the manifold and turbine housing to expand. The manifold to housing coupling must be designed to account for and permit such thermal expansion. At the same time, the coupling must minimize any obstruction to air flow. Traditional designs fail to adequately account for thermal expansion while also maximizing smooth airflow through the system.
Therefore, an improved manifold to turbine housing connection is needed.